This incredible picture is a combination of green, red, and near-infrared filtered images (displayed a bit confusingly as magenta, green, and red respectively in the image above). The three galaxies are all spirals at varying degrees of tilt: M 66 at the lower right is the most open, NGC 3628 is almost exactly edge-on, and M 65 at the upper right is intermediate. Look at how prominent the central dust lane is in NGC 3628!
I've seen M 65 and 66 with my own telescope back when I was in high school, and I spent a lot of hours at the end of my driveway poking around the sky. They're pretty bright, but oddly I don't remember seeing NGC 3628. I wonder what I would have made of it? Now, with a couple of decades experience under my belt, I can see that the three galaxies are interacting: NGC 3628 has an inflated, puffy disk, and the you can see that wide-flung arm of M66. Those are clear signs the gravity of each of these galaxies is affecting the others.
Hubble snapped an amazing close-up shot of M66 last year, but there is something majestic and lovely about this wider, deeper picture. It really puts the galaxies in context, and astronomers can use that to see precisely how the galaxies are interacting. As usual, the marriage of science and beauty is clear and gorgeous when staged upon the sky.